Surface characteristics, reliability, and failure mechanisms of tin/lead, copper, and gold metallizations

Abstract

In this paper, surface characteristics, microstructure, reliability and failure mechanisms of tin/lead, copper and gold metallizations for conductive adhesive joining have been studied. Electron spectroscopy for chemical analysis (ESCA) and Auger electron spectroscopy (AES) have been used to analyze Sn37Pb, copper and gold metallizations. The analyzes show that copper and nickel may be present as impurities on the gold plated surface. The tin and lead oxides present on the Sn37Pb plated surface were found to be 74 /spl Aring/ and 26 /spl Aring/, respectively. The microstructures were studied using scanning and transmission electron microscopy (SEM and TEM). The chemical analysis of the consisting compounds were analyzed using energy dispersive X-ray analysis (EDX). The conductive adhesive joints were exposed to constant humidity treatment at 85/spl deg/C, 85% RH up to 2000 h. The mechanical and electrical performance were measured using a shear tester and an Ohmmeter after various humidity treatment times. After the 85/spl deg/C/85% RH treatment, an increase in electrical resistance of the copper joints was found with increasing testing time due to the formation of Cu/sub 2/O. Also, there was a decrease in mechanical strength and an increase in electrical resistance due to oxidation of Pb. The best electrical performance was observed on the gold metallization after the constant humidity test.